eqwidth is an IRAF task in the rvsao package which computes equivalent widths for absorprtion or emission lines. It is based on the IRAF task noao.onedspec.sbands, but allows you to compute equivalent widths for any band of a multispec spectrum and redshifts the given rest wavelength regions based on the value of the VELOCITY or APVEL header keyword.

We have found that automatic cosmic ray rejection in extraction of a spectrum from a 2-D image can change the equivalent width of some lines. We recommend using uncleaned spectra for equivalent widths in such situations. That would be the second spectrum in IRAF multispec files which have been cleaned, the third being the background which was removed, and the fourth being the raw extracted spectrum.


eqwidth spectra



Last updated April 11, 2003 by Doug Mink dmink@cfa.harvard.edu

Telescope Data Center [rvsao] [xcsao] [emsao] [sumspec] [linespec] [eqwidth]